Nearly nine years ago, massive crowds marched through the streets of Iran's major cities demanding change, in the first major challenge to the rule of hard-line Muslim clerics since they came to power in 1979.

Nearly nine years ago, massive crowds marched through the streets of Iran's major cities demanding change, in the first major challenge to the rule of hard-line Muslim clerics since they came to power in 1979.

The move was sparked in the summer of 2009 when the reformist opposition claimed the re-election victory of Mahmoud Ahmadinejad was rigged. Millions of people protested nationwide over the next months, in what became known as the "Green Movement".

The crackdown by authorities was brutal. The elite Revolutionary Guard and their volunteer force, known as the Basij, opened fire on marchers and carried out a wave of arrests. Dozens of protesters were killed, many more were jailed and tortured, and the movement's political leadership was put under house arrest.

Now, Iran's Islamic Republic is seeing a new wave of unrest. This time it appears more spontaneous, fuelled by anger over a still-faltering economy, unemployment and corruption. The movement is most commonly referred to on social media as "Protests Everywhere".

Here is a look at the differences between the protests of 2009 and today.

:: WHO'S PROTESTING?

In 2009, the demonstrations swelled to hundreds of thousands and were focused on Iran's main cities and provincial capitals, including Tehran, Tabriz, Isfahan and Shiraz.

In contrast, the past days' fury has burst out mainly in mid-sized cities and towns. The protests have been smaller - in the hundreds or, at most, a few thousand - but they have swiftly erupted in far more places compared with eight years ago.

The first protest, sparked by a rise in egg and poultry prices, broke out in Mashhad, a city in the east that is considered a stronghold for conservatives. Unrest quickly spread across dozens of towns throughout the country. These sorts of mid-sized communities in the provinces have suffered heavily from the poor economy, with large proportions of young people unemployed and mired in despair over the future.

:: REJECTING THE SYSTEM

The protests may be rooted in anger over the economy and corruption, but protesters quickly started chanting slogans directly against Supreme Leader Ayatollah Ali Khamenei and denouncing the Islamic Republic itself - not just a call for reforms, but an open and outright rejection of the ruling system.

This is a dramatic shift from 2009. Protesters then had major demands - they wanted Mr Ahmadinejad's re-election overturned, reformist leader Mir Hossein Mousavi installed as president, greater social freedoms, and an end to the security forces' tight oppression.

But their demands largely stayed within the framework of existing politics. Some voices called for Khamenei's removal, but they were limited; the Green Movement's leaders went out of their way to say they were not aiming to bring down the system, whether out of pragmatism or faith in the potential for the "republic" part of "Islamic Republic".

Now, videos show some protesters chanting: "Death to the dictator" and calling for the end of the nearly 40-year-old Islamic Republic. This reflects how many now see families of prominent cleric-politicians and Iran's paramilitary Revolutionary Guard as a corrupt economic elite, monopolising business, hoarding wealth and leaving ordinary people with no place in the economy.

The protests have revealed a hidden vein of sentiment - and not just among a "westernised" urban elite - which has lost hope over clerical rule and now openly wants to remove it.

:: LEADERSHIP

The Green Movement of 2009 was firmly rooted in the reformist political movement, symbolised by former president Mohammad Khatami, the would-be president Mr Mousavi and other prominent politicians who advocated greater margins of freedom and opening to the west.

That gave the protests a base and organisation able to mobilise massive numbers. It also gave protesters a defined set of demands.

So far, no clear leadership has emerged for "Protests Everywhere". Even opposition activists in Tehran are unsure who are involved. The marches - with videos showing crowds of largely young men and women - have proven persistent and organised. Supporters on social media say this shows the breadth of support for the leaderless popular movement.

:: REFORMERS AND HARD-LINERS

In 2009, hard-liners were in firm control. Mr Ahmadinejad's policies and abrasive manner galvanised opposition - even part of the clerical establishment was against him - which gave a wide base of support for protests.

Now, the constituency that would be expected to join marches is more uncertain.

A relative moderate, Hassan Rouhani, is president, brought into office by the votes of reformists. Many of those voters now feel his controversial nuclear deal with the west has failed to bring in the economic benefits he promised.

If large numbers decide there is no hope in the system and turn to the streets, it could push the protests into the scale of 2009. But many may hesitate, calculating that an uprising will plunge Iran into the unknown and that trying for gains under Mr Rouhani is safer.

The ferocity of the 2009 crackdown traumatised the opposition. The state showed it was prepared to unleash lethal force, and many activists were relentlessly harassed and persecuted for years afterwards. Mr Mousavi and other Green Movement leaders have been under house arrest for years, which makes many wary of taking to the streets again.

Mr Rouhani has so far advocated a softer hand, saying Iranians have a right to protest. Reform politicians are calling for changes in economic policy to defuse the unrest. But ultimately, as in 2009, it will be Khamenei and the Revolutionary Guard that decide - and if they sense the unrest is growing out of control, they could unleash a brutal and bloody response.

:: SOCIAL MEDIA

When Neda Agha Soltan was shot dead during one of the 2009 protests in Tehran, the 26-year-old woman became an icon of the uprising. Video footage of her last moments circulated widely on Twitter and other social media. It was a cycle that fed the protests. Young men and women were killed, but the images of their deaths inspired others to join.

In the context of 2009, Twitter had only been launched three years earlier. Facebook was only a little bit older. At the time, fewer than one million Iranians had smart phones.

Now, the reach has been exponentially magnified. Today, an estimated 48 million Iranians have smart phones, more than half the population. Social media apps have flourished - besides Instagram, the messaging apps Telegram and WhatsApp are very popular. They are also encrypted, providing a degree of protection from state surveillance and becoming a major organising tool and a space for images and videos to circulate.

However, 2009 in Iran and the 2011 Arab Spring uprisings also showed the limits of social media. Organisation and imagery in the virtual realm do not always translate into effectiveness on the ground.

:: INTERNATIONAL BACKGROUND

President Donald Trump is an unpredictable new factor. Mr Trump has dismissed what he portrayed as a weak response by then-president Barack Obama to the 2009 protests. Critics contend Mr Obama should have thrown US weight behind the uprising in an effort to bring down the Iranian government.

But Mr Trump faces the same question his predecessor did: how much effect can the United States really have on the ground? Too close an association with the US and with Mr Trump could discredit the protests in the eyes of some Iranians.

So far, the rhetoric from the US administration has mirrored Mr Obama's - both demanding that Iran should allow free expression and warning that "the world is watching".

The US state department also raised the possibility of new sanctions on Iran over any crackdown on protesters.